High order structure functions and intermittency in decaying rotating turbulence

Longitudinal and transverse velocity structure functions are measured in a decaying rotating turbulence experiment by means of Particle Image Velocimetry (PIV). Turbulence is generated by rapidly towing a grid through the fluid, providing an initial state which is approximately homogeneous and isotropic. During the self-similar decay of turbulence, before the Ekman timescale, structure functions up to order 8 show well-defined power laws in the inertial range. For moderate Rossby numbers, the exponent of the second-order longitudinal structure function, $\zeta_2$, is found to increase in time, in agreement with the steepening of the power spectrum, but the normalized higher-order exponents, $\zeta_p / \zeta_2$, remain close to those of the intermittent non-rotating case (She-Leveque model). For smaller Rossby numbers, a slight departure of $\zeta_p / \zeta_2$ from the intermittent curve is observed, although it remains far from the non-intermittent linear prediction $\zeta_p / \zeta_2 = p/2$. These results are compared to recent experiments and simulations of forced rotating turbulence.